Middle ear prosthesis

Details Middle ear prosthesis Middle ear prosthesis

1999-07-13

2001-06-05

Isabella, David (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Ear or nose prosthesis

Reexamination Certificate

active

06241767

ABSTRACT:

BACKGROUND AND SUMMARY OF THE INVENTION
1. Field of the Invention
The invention relates to a middle ear prosthesis with a tubular housing. The prosthesis replaces eardrum (tympanic membrane) and ossicles of the middle ear which have been destroyed by otitis or similar.
2. Description of the Prior Art
It is presently known to repair the sound receiving and conducting mechanismus of the middle ear by surgical implantation of various types of prosthesis. Such repair involves total reconstruction of all three ossicles and the ear drum.
Such a middle ear prosthesis is known out of DE 4 407 847 A1. The tubular housing of this prosthesis is not only closed at its outwards showing end by an outer membrane replacing the eardrum. It is also provided at its inner end with an inner membrane. Said inner membrane is joined to the outer membrane by a transmission link that is located inside and that prestresses inwards outer and inner membrane. The surface of the outer membrane is bigger than the surface of the inner membrane. Sound transmission from the inner membrane to the stapes base plate occurs by a small quantity of the patient's own fat. This fat required for sound transmission is located outside the prosthesis between the inner membrane and the stapes base plate.
A disadvantage of this known middle ear prosthesis is that the achievable sound pressure at the stapes base plate is not high enough for normal hearing, since the transformation ratio of the two membranes is reduced. Furtheron the transmission path of the sound between the inner membrane and stapes base plate is subject to unsteadiness since the smallest inclusion of air in the fat or its dwindling and the thus occurring smallest air gap are already strongly influencing the transmission of sound.
EP 460 354 B1 discloses a middle ear prosthesis that does without its own housing. The artificial eardrum is tentered in an outer retaining ring inserted in a recess made especially for said ring in the petrous bone. The eardrum has a hole in its centre into which a thickened front area of an ossicle-substitute may be fitted. Thus, the ossicle-substitute may in a first place be arranged in the space behind the artificial eardrum. Then, the artificial eardrum is inserted, whereas the front end of the ossicle-substitute snaps into the hole of the eardrum.
Further middle ear prostheses are known out of EP 281 047 B1, DE 2 905 183 C3, DE 2 937 842 C3 and EP 203 785 B1.
SUMMARY OF THE INVENTION
The present invention overcomes the mentioned problems with the middle ear prosthesis by providing that the sound pressure prevailing in the inner ear is sufficient and that the sound transmission to the inner ear is guaranteed to be always secure and durable.
The middle ear prosthesis according to the invention replaces the function of the sound transmitting apparatus of a natural middle ear as completely as possible. It is hereby not depending on the function of the natural eustachian tube and/or the mucosa of the middle ear cavities.
The middle ear prosthesis according to the invention is used in the attendance of patients with chronic otitis media that durably weakens or hinders a normal sound transmission. Other afflictions with said same consequence are for example mucosal suppuration in the middle ear, suppuration of the bone in the middle ear (=suppuration of a cholesteatoma), chronic perturbation in the aeration of the auditory tube, malformations of the middle ear, permanent destructions of the sound conducting apparatus by trauma and tumours, etc. The middle ear prosthesis is depending neither on a mucosa lining nor on an aeration of the auditory tube. It consists of a housing divided for example in two parts that may at least be closed so as to be germ-tight. The inner space of the housing is thus safe against germs trying to penetrate from the outside.
The housing is provided with a holding device that temporarily fastens the ossicle part called hereinafter first ossicle part. Said holding device is removed, cut apart or otherwise discharged later, before the operation comes to an end. It may also be kept if it is flexible enough.
The first ossicle part is inserted through an artificial opening in the stapes base plate and directly stimulates the inner ear or it is placed onto this base plate. The direct sound transmission to the inner ear is thus assured. The loss of coupling fat or the like can no more be detrimental to said sound transmission.
The first ossicle part is moved by the artificial ear drum and/or by an electric actuation, particularly an electrodynamic or piezoelectric actuation. Such an electric actuation gets its tension from an amplifier, for example from the amplifier of a hearing aid.
During the operation, the inner space of the housing may be reached through the window. It allows the necessary manipulations inside the housing. Particularly the holding device may be reached through the window. Said window is closed by the cover part so as to be germ-tight.
The window may have different versions. The window may for example be provided between two parts of a housing consisting of a transmission part and a coupling part, whereas recesses or indentations on the edge side are provided in the overlapping area of the two parts. Said recesses are forming the window when positioned in a certain rotary position relative to one another, whereas, in another rotary position, they are closing completely. Housings consisting of three and more parts are also possible, the third and possibly further parts being allocated for constituting or locking a window area, for example by an axial slidable cylinder. Annular, cylindrical parts that are rotatable relative to the coupling part and/or transmission part and that have a window just as said part are also provided. The window may be either released or completely locked by rotation.
During the operative insertion of the middle ear prosthesis, the coupling part is inserted first and is attached in the best possible way to the wall of the eardrum around the oval window. It has proved to be particularly preferential to imitate as accurately as possible the course of the individual relief of the medial eardrum wall of the patient wearing the middle ear prosthesis when designing the free end area of the coupling part. A good adaptation to the eardrum wall is thus achieved which makes it possible to obtain, using appropriate connecting material, a proper closing and a secure fastening of the coupling part on the eardrum wall.
When the coupling part is inserted, in case of an opening in the stapes base plate, said opening is either already provided or it is arranged only then. It is preferably made by means of a laser. It is just big enough for the first ossicle part to fit through it. The first ossicle part is preferably a thin wire made of titanium or gold. The first ossicle part is fixed on the holding device or has already been fixed to it. The fixation is made in such a way that the first ossicle part is projecting into the inner ear to a desired extent. The fixation guarantees that the projection will neither fall short of nor exceed said extent.
It has proven to be particularly advantageous for the housing of the middle ear prosthesis according to the invention to seal the surrounding tissue in a germ-tight, preferably hermetic way. Thus, the inner space of the housing is securely protected against the penetration of germs.
The location and size of the housing of the middle ear prosthesis have well enough been determined by considerable measurements done on petrous bone preparations. Typically, an average maximal diameter of approximately 11 mm and a maximum length of approximately 20 mm have been found.
The housing preferably consists of the coupling part and of a transmission part, both being provided with connecting means for their junction to one another and to the housing. The transmission part is preferably provided with a second ossicle part. During the operational insertion, the connection between the two ossicle parts may be observed and preferably executed thro

Affiliated with

Also associated with

Rating

Middle ear prosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Middle ear prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Middle ear prosthesis will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2506981